The present invention is directed to the imaging of objects with x-rays, particularly to grids utilized in the imaging apparatus to block scattered radiation, and more particularly to an air-core grid, and a process for fabricating same, using glass containing a high atomic number oxide, such as lead, constructed to provide a large fraction of the area open for allowing imaging radiation to pass through.
When imaging objects or parts of the human body, the quality of the image is compromised by scattered x-rays. Mechanical devices, called grids, are used to attempt to block the scattered radiation while allowing the desired imaging radiation to pass through. One common device for this purpose aligns foils of highly attenuating material, such as lead, such that the desired x-rays can pass between the foils while scattered x-rays are blocked because they arrive at different angles from the imaging radiation. To maintain alignment of the foils, a spacer material is used that is relatively transparent to the desired x-rays. This spacer material is usually paper, carbon, or aluminum.
Another prior grid arrangement involves vanes whose axes are parallel. A more recent approach, is a grid structure as described and claimed in copending application Ser. No. 08/051,228 filed Apr. 23, 1993, entitled "High Performance X-Ray Anti-Scatter Grid", and assigned to the same assignee. This grid arrangement involved a plurality of parallel or crossed slots formed in a substrate having low x-ray capacity and coated or filled with a material having high x-ray opacity whereby the scattered x-rays are blocked from entering the grid.
When imaging the human body with x-rays, such the chest area and imaging breasts for early detection of breast cancer, scattered radiation degrades the image. This is especially true when film is used to record or recapture the image for subsequent display on a light box. Film has an extremely limited dynamic range and the human eye/brain has a very limited ability to resolve differences in darkness in the image. The scattered radiation uses up a significant portion of the dynamic range of the film and reduces the contrast in the resulting image, making it more difficult or even impossible for the human eye to visualize disease, injury or abnormality. The scattered radiation also adds quantum noise to the image, thereby further degrading its diagnostic power.
While numerous prior approaches to solving the scattered radiation problem, including the use of various types of grids, as disccused above, a need still exists for a device which can allow the desired x-rays to pass through efficiently while blocking the undesired scattered x-rays. This is accomplished by the present invention which involves the formation of an air-core grid for scattered x-ray rejection. This is accomplished by using a grid composed of material such as glass containing lead oxide constructed in a pattern to block the scattered x-rays, with the desired imaging x-rays passing through open areas in the grid pattern, with grid being composed of about 80% open area. Thus, the grid of this invention also eliminates the prior used spacer material that is transparent to the desired x-rays.